U.S. patent application number 10/946264 was filed with the patent office on 2006-03-23 for opto-electronic processors with reconfigurable chip-to-chip optical interconnections.
Invention is credited to Michael G. Lee, Kishio Yokouchi.
Application Number | 20060062512 10/946264 |
Document ID | / |
Family ID | 36074089 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060062512 |
Kind Code |
A1 |
Lee; Michael G. ; et
al. |
March 23, 2006 |
Opto-electronic processors with reconfigurable chip-to-chip optical
interconnections
Abstract
Disclosed are reconfigurable optical interconnections for
opto-electronic processors in general, and for scalable computer
architectures and scalable network servers in particular. The
optical-signal interconnects are adaptable, or reconfigurable,
during the normal operation of the processor. A large number of
optical-signal interconnects may be provided among the components
of the processor while using a small number of light transmitters
and/or light receivers.
Inventors: |
Lee; Michael G.; (San Jose,
CA) ; Yokouchi; Kishio; (Tokyo, JP) |
Correspondence
Address: |
SHEPPARD, MULLIN, RICHTER & HAMPTON LLP
333 SOUTH HOPE STREET
48TH FLOOR
LOS ANGELES
CA
90071-1448
US
|
Family ID: |
36074089 |
Appl. No.: |
10/946264 |
Filed: |
September 20, 2004 |
Current U.S.
Class: |
385/15 ; 385/14;
385/31; 385/88; 385/89 |
Current CPC
Class: |
G02B 6/4214 20130101;
G02F 1/315 20130101; G02B 6/12002 20130101; G02B 6/43 20130101 |
Class at
Publication: |
385/015 ;
385/088; 385/089; 385/014; 385/031 |
International
Class: |
G02B 6/26 20060101
G02B006/26; G02B 6/12 20060101 G02B006/12; G02B 6/36 20060101
G02B006/36; G02B 6/42 20060101 G02B006/42 |
Claims
1. A processor comprising: at least a first IC chip, a second IC
chip, and a third IC chip, each IC chip being mounted on a
substrate; a first light transmitter that receives a first
electrical signal from the first IC chip and generates an optical
signal at an optical output in relation to the first electrical
signal; a first light receiver having an optical input and
generating a second electrical signal in relation to the amount of
light received at its optical input, the second electrical signal
being electrically coupled to the second IC chip; a second light
receiver having an optical input and generating a third electrical
signal in relation to the amount of light received at its optical
input, the third electrical signal being electrically coupled to
the third IC chip; and a first optical deflector having an optical
input coupled to the optical output of the first light transmitter
to receive an optical signal therefrom, a first optical output
optically coupled to a first output waveguide that enables light to
be conveyed to the first light receiver, a second optical output
optically coupled to a second output waveguide that enables light
to be conveyed to the second light receiver, and an electrical
input that receives a first control signal in electrical form, the
first optical deflector coupling the optical signal received at its
optical input more to its first optical output than its second
optical output when the first control signal has a first state, and
more to its second optical output than its first optical output
when the first control signal has a second state.
2. The processor of claim 1 wherein at least two IC chips are
mounted on a common substrate.
3. The processor of claim 1 wherein each IC chip is mounted on a
respective substrate.
4. The processor of claim 1 wherein the first control signal is
generated by the first IC chip.
5. The processor of claim 1 wherein the first IC chip is disposed
on a first substrate, and wherein the first control signal is
generated by fifth IC chip disposed on the first substrate.
6. The processor of claim 5 wherein said second IC chip transmits a
second control signal to the fifth IC chip requesting that the
first control signal be generated in its first state.
7. The processor of claim 6 wherein the second control signal is in
electrical form.
8. The processor of claim 1 further comprising: a second light
transmitter; a second optical deflector having a first optical
input optically coupled to a waveguide that enables light to be
conveyed from the first light transmitter, a second optical input
optically coupled to a waveguide that enables light to be conveyed
from the second light transmitter, an optical output optically
coupled to the optical input of the first light receiver, a first
optical coupling efficiency between its first optical input and its
optical output, a second optical coupling efficiency between its
second optical input and its optical output, and an electrical
input that receives a second control signal in electrical form, the
second optical deflector making the first optical coupling
efficiency greater than the second optical coupling efficiency when
the, second control signal has a first state, and making the second
optical coupling efficiency greater than the first optical coupling
efficiency when the second control signal has a second state.
9. The processor of claim 1 wherein the first optical deflector
comprises: an input waveguide having a first end for receiving
light from the first light transmitter and a second end; and a
prism deflector having a first optical surface facing towards the
second end of the input waveguide to receive light therefrom, a
second optical surface to enable light to exit the prism deflector
in a plurality of directions, a body of opto-electric material
disposed between the first and second optical surfaces, and at
least one electrode electrically coupled to the electrical input to
receive the first control signal from an IC chip, wherein the at
least one electrode is disposed between the first and second
optical surfaces on a surface of the body of opto-electric
material; and wherein the first output waveguide has a first end
facing towards the second optical surface of the prism deflector
and a second end; and wherein the second output waveguide has a
first end facing towards the second optical surface of the prism
deflector and a second end.
10. The processor of claim 9 further comprising a reflector
disposed at the first end of the input waveguide.
11. The processor of claim 1 wherein the first optical deflector,
the first output waveguide, and the second output waveguide are
disposed on a common substrate; wherein the first output waveguide
has a first end, a second end, and an optical propagation axis;
wherein the second output waveguide is disposed above the first
output waveguide and has a first end, a second end, and an optical
propagation axis, the first end being closer to the first end of
the first output waveguide than the second end of the first output
waveguide; and wherein the first optical deflector comprises: an
angled reflector disposed to couple light to the first end of the
first output waveguide and having a beveled surface with respect to
the optical propagation axis of the first output waveguide; and a
variable reflector having a top surface disposed to receive light
from the light transmitter, a bottom surface, and a first side
surface positioned to couple light toward the first end of the
second output waveguide, the variable reflector further having a
first body of electro-optic material disposed between the top and
bottom surfaces of the variable reflector, a second body of
material disposed between the top and bottom surfaces of the
variable reflector and further disposed between the first body of
electro-optic material and the first side surface, and an interface
surface between the first and second bodies, the interface surface
forming a bevel angle with respect to the optical propagation axis
of the second output waveguide, the second body of material having
a refractive index that is higher than the intrinsic refractive
index of the first body of material, the variable reflector further
comprising at least one electrode electrically coupled to the
electrical input to receive the first control signal from an IC
chip and located to generate a corresponding electric field in
first body of electro-optic material; and wherein the variable
reflector couples the light received from the light transmitter
more to its bottom surface than its first side surface when the
first control signal has a first state, and more to its first side
surface than its bottom surface when the first control signal has a
second state; and wherein the first end of the second output
waveguide is disposed to receive light emitted from the side
surface of the variable reflector; and wherein the angled reflector
is disposed to receive light emitted from the bottom surface of the
variable reflector.
12. A processor comprising: at least a first IC chip, a second IC
chip, and a third IC chip, each IC chip being mounted on a
substrate; a first light receiver having an optical input and
generating a first electrical signal in relation to the amount of
light received at its optical input, the first electrical signal
being electrically coupled to the first IC chip; a first light
transmitter that receives a second electrical signal from the
second IC chip and generates an optical signal at an optical output
in relation to the second electrical signal; a second light
transmitter that receives a third electrical signal from the third
IC chip and generates an optical signal at an optical output in
relation to the third electrical signal; and a first optical
deflector having a first optical input optically coupled to a first
input waveguide that enables light to be conveyed from the first
light transmitter, a second optical input optically coupled to a
second input waveguide that enables light to be conveyed from the
second light transmitter, an optical output optically coupled to
the optical input of the first light receiver, a first optical
coupling efficiency between its first optical input and its optical
output, a second optical coupling efficiency between its second
optical input and its optical output, and an electrical input that
receives a first control signal in electrical form, the first
optical deflector making the first optical coupling efficiency
greater than the second optical coupling efficiency when the first
control signal has a first state, and making the second optical
coupling efficiency greater than the first optical coupling
efficiency when the first control signal has a second state.
13. The processor of claim 12 wherein the first optical deflector
making the first optical coupling efficiency substantially equal to
the second optical coupling efficiency when the electrical control
signal has a third state.
14. The processor of claim 12 wherein at least two IC chips are
mounted on a common substrate.
15. The processor of claim 12 wherein each IC chip is mounted on a
respective substrate.
16. The processor of claim 12 wherein the first control signal is
generated by the first IC chip.
17. The processor of claim 12 further comprising: a second light
receiver having an optical input and generating a first electrical
signal in relation to the amount of light received at its optical
input; and a second optical deflector having an optical input
coupled to the optical output of the first light transmitter to
receive an optical signal therefrom, a first optical output
optically coupled to a first output waveguide that enables light to
be conveyed to the first light receiver, a second optical output
optically coupled to a second output waveguide that enables light
to be conveyed to the second light receiver, and an electrical
input that receives a second control signal in electrical form, the
second optical deflector coupling the optical signal received at
its optical input more to its first optical output than its second
optical output when the second control signal has a first state,
and more to the second optical output than the first optical output
when the second control signal has a second state.
18. The processor of claim 12 wherein the first optical deflector
comprises: an output waveguide having a first end for coupling
light to the first light receiver and a second end; and a prism
deflector having a first optical surface facing towards the second
end of the output waveguide to provide light thereto, a second
optical surface facing towards the first optical surface couple
light to the prism deflector from a plurality of directions, a body
of opto-electric material disposed between the first and second
optical surfaces, and at least one electrode electrically coupled
to the electrical input to receive the first control signal from an
IC chip, wherein the at least one electrode is disposed between the
first and second optical surfaces on a surface of the body of
opto-electric material; and wherein the first input waveguide has a
first end facing towards the second optical surface of the prism
deflector and a second end; and wherein the second input waveguide
has a first end facing towards the second optical surface of the
prism deflector and a second end.
19. The processor of claim 18 further comprising a reflector
disposed at the first end of the output waveguide.
20. The processor of claim 12 wherein the first optical deflector,
the first input waveguide, and the second input waveguide are
disposed on a common substrate; wherein the first input waveguide
has a first end, a second end, and an optical propagation axis;
wherein the second input waveguide is disposed above the first
input waveguide and has a first end, a second end, and an optical
propagation axis, the first end being closer to the first end of
the first input waveguide than the second end of the first input
waveguide; and wherein the first optical deflector comprises: an
angled reflector disposed to couple light from the first end of the
first input waveguide and having a beveled surface with respect to
the optical propagation axis of the first input waveguide; and a
variable reflector having a top surface disposed to provide light
to the light receiver, a bottom surface, and a first side surface
positioned to couple light from the first end of the second input
waveguide, the variable reflector further having a first body of
electro-optic material disposed between the top and bottom surfaces
of the variable reflector, a second body of material disposed
between the top and bottom surfaces of the variable reflector and
further disposed between the first body of electro-optic material
and the first side surface, and an interface surface between the
first and second bodies, the interface surface forming a bevel
angle with respect to the optical propagation axis of the second
input waveguide, the second body of material having a refractive
index that is higher than the intrinsic refractive index of the
first body of material, the variable reflector further comprising
at least one electrode electrically coupled to the electrical input
to receive the first control signal from an IC chip and located to
generate a corresponding electric field in first body of
electro-optic material; and wherein the first end of the second
input waveguide is disposed to couple light to the side surface of
the variable reflector; and wherein the angled reflector is
disposed to couple light to the bottom surface of the variable
reflector; and wherein the variable reflector has a first optical
coupling efficiency between the top surface of the variable
reflector and the first side surface of the variable reflector, and
a second optical coupling efficiency between the top surface of the
variable reflector and the bottom surface of the variable
reflector, wherein the variable reflector makes the first optical
coupling efficiency greater than the second optical coupling
efficiency when the control signal has a first state, and makes the
second optical coupling efficiency greater than the first optical
coupling efficiency when the control signal has a second state.
21. An optical deflector comprising: a first waveguide having a
first end, a second end, and an optical propagation axis; a second
waveguide disposed above the first waveguide and having a first
end, a second end, and an optical propagation axis, the first end
being closer to the first end of the first waveguide than the
second end of the first waveguide; an angled reflector disposed at
the first end of the first waveguide and having a beveled surface
with respect to the optical propagation axis of the first
waveguide; and a variable reflector having a top surface to receive
or transmit light therefrom, a bottom surface, and a first side
surface, the variable reflector further having a first body of
electro-optic material disposed between the top and bottom surfaces
of the variable reflector, a second body of material disposed
between the top and bottom surfaces of the variable reflector and
further disposed between the first body of electro-optic material
and the first side surface, and an interface surface between the
first and second bodies, the interface surface forming a bevel
angle with respect to the optical propagation axis of the second
waveguide, the second body of material having a refractive index
that is higher than the intrinsic refractive index of the first
body of material, the variable reflector further comprising at
least one electrode for receiving a control signal and located to
generate an electric field in first body of electro-optic material
in relation to the control signal.
22. The optical deflector of claim 21 wherein the optical deflector
receives light at the top surface of the variable reflector,
wherein the variable reflector couples the received light received
more to its bottom surface than its first side surface when the
control signal has a first state, and more to its first side
surface than its bottom surface when the control signal has a
second state; and wherein the first end of the second waveguide is
disposed to receive light emitted from the first side surface of
the variable reflector, and wherein the angled reflector is
disposed to receive light emitted from the bottom surface of the
variable reflector.
23. The optical deflector of claim 21 wherein the variable
reflector has a first optical coupling efficiency between the top
surface of the variable reflector and the first side surface of the
variable reflector, and a second optical coupling efficiency
between the top surface of the variable reflector and the bottom
surface of the variable reflector, wherein the variable reflector
makes the first optical coupling efficiency greater than the second
optical coupling efficiency when the control signal has a first
state, and makes the second optical coupling efficiency greater
than the first optical coupling efficiency when the control signal
has a second state.
24. The optical deflector of claim 23 wherein the variable
reflector makes the first optical coupling efficiency substantially
the same as the second optical coupling efficiency when the control
signal has a third state.
25. The optical deflector of claim 21 wherein the interface surface
is planar.
26. The optical deflector of claim 21 wherein the bevel angle is
between 43 degrees and 47 degrees.
27. The optical deflector of claim 21 wherein the variable
reflector further comprises a second side surface, a third side
surface, and a second electrode, wherein the at least one electrode
is disposed on the second side surface adjacent to the first body
of electro-optic material, and wherein the second electrode is
disposed on the third side surface adjacent to the first body of
electro-optic material.
28. The optical deflector of claim 21 wherein the refractive index
of the second body of material is higher than the intrinsic
refractive index of the first body of material by at least 10%.
29. The optical deflector of claim 21 wherein the refractive index
of the second body of material is higher than the intrinsic
refractive index of the first body of material by at least 20%.
30. The optical deflector of claim 21 wherein the refractive index
of the second body of material is higher than the intrinsic
refractive index of the first body of material by at least 25%.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to opto-electronic processors
with chip-to-chip optical interconnections suitable for use in
scalable computer architectures and scalable network servers. More
particularly, the present invention relates, to opto-electronic
processors with adaptable chip-to-chip optical
interconnections.
BACKGROUND OF THE INVENTION
[0002] Mainstay computer systems and network-server systems use
electrical interconnects among the integrated-circuit (IC) chips on
the component boards, and electrical interconnects on bus-based
interconnect planes to interconnect the component boards. The speed
of communication in these systems is limited both by the well-known
"skin effect," where resistance increases as signal frequency
increases, and by capacitance effects. To overcome the resistance
and capacitance of the electrical interconnects, more powerful bus
drivers have been used. However, these drivers increase the power
consumption of the system, and require additional cooling for the
system.
[0003] Recently, there has been an explosive growth in the amount
of information conveyed through the Internet, local networks, and
high-speed data exchanges between servers. Current information
processing systems and network servers are having difficulty
keeping up with the growth, and are now running into the physical
limits of the electronic components, electric interconnections, and
assembly technologies.
[0004] The present invention is directed to addressing the ability
of information processing systems and network servers to keep up
with the growth of information communication, and to addressing the
physical limits placed on systems by current electronic components,
electric interconnections, and assembly technologies.
SUMMARY OF THE INVENTION
[0005] As part of making their invention, the inventors have
recognized that the board-to-board electrical interconnects between
component boards could be replaced by optical-signal interconnects.
The propagation of optical signals is not limited by resistance,
capacitance, or the skin effect, and a light beam only generates a
small amount of heat dissipation due to light absorption in
waveguides and the light receiver. However, the inventors have
recognized that directly replacing each board-to-board electrical
interconnect with an optical-signal interconnect would require a
dedicated light transmitter device on one board, a dedicated light
receiver device on another board, and a dedicated configuration of
one or more optical waveguides between the light transmitter device
and the light receiver device. Scalable-architecture computer
systems and blade-type network servers have large numbers of
board-to-board electrical interconnects, and thus the replacement
of electrical interconnects with optical-signal interconnects would
require large numbers of light transmitters and light receivers
incorporated onto each component board. This would greatly increase
the size and expense of each component board, calling into question
the viability and cost-effectiveness of using optical-signal
interconnects in scalable-architecture computer systems and
blade-type network servers.
[0006] As a further part of making their invention, the inventors
have discovered that many scalable-architecture computer systems
and blade-type network servers have a relatively low utilization of
their board-to-board electrical interconnects. That is, while each
component board of such a system has several electrical
interconnects to each of the other component boards, a much smaller
number of the electrical interconnects are used at any one time.
Moreover, when an electrical interconnect is used, it tends to be
used intensely for a substantial period of time, and then goes idle
for a substantial period of time before being used again.
[0007] As part of making their invention, the inventors have
recognized that the implementation of board-to-board optical-signal
interconnects can be made viable and cost-effective by using a
smaller number of optical-signal interconnects (compared to the
number of electrical interconnects being replaced), and by making
the optical-signal interconnects adaptable, or reconfigurable,
during the normal operation of the computer system or network
server. As an example, instead of using three light transmitters on
a component board to replace three board-to-board electrical
interconnects to three other component boards, a single light
transmitter is used, and its output is guided to one of three
waveguides (or possibly two of three waveguides, or three of three
waveguides) by an optical deflecting device that is under the
control of the component board. Similarly, instead of using three
light receivers on a component board to replace three
board-to-board electrical interconnects to three other component
boards, a single light receiver is used and its input is optically
coupled to one of three waveguides by another optical deflecting
device that is under the control of the component board.
[0008] Accordingly, a first exemplary embodiment of the present
invention encompasses a processor that is suitable for use as a
computer system, or a network server, or the like. The processor
comprises at least a first IC chip, a second IC chip, and a third
IC chip, each IC chip being mounted on a substrate, such as a
component board. Usually, the IC chips are mounted on separate
substrates, but two or more of the IC chips may be mounted on a
common substrate. The IC chips perform tasks in support of the
operation of the processor, the first IC chip generating a signal
that is to be conveyed to either of the second and third IC chips.
The processor further comprises a first light transmitter that
receives a first electrical signal from the first IC chip, and that
generates an optical signal at an optical output in relation to the
first electrical signal. The first light transmitter may be
integrated onto the first IC chip, or it may be integrated onto
another chip. The processor further comprises a first light
receiver having an optical input and generating a second electrical
signal in relation to the amount of light received at its optical
input. The second electrical signal is electrically coupled to the
second IC chip, and the first light receiver may be integrated onto
the second IC chip or another chip. The processor further comprises
a second light receiver having an optical input and generating a
third electrical signal in relation to the amount of light received
at its optical input. The third electrical signal is electrically
coupled to the third IC chip, and the second light receiver may be
integrated onto the third IC chip or another chip. The processor
further comprises an optical deflector having an optical input
optically coupled to the optical output of the first light
transmitter to receive an optical signal therefrom, a first optical
output optically coupled to a first output waveguide that enables
light to be conveyed to the first light receiver, a second optical
output optically coupled to a second output waveguide that enables
light to be conveyed to the second light receiver, and an
electrical input that receives a first control signal in electrical
form. The optical deflector couples the received optical signal
more to the first output waveguide than the second output waveguide
when the electrical control signal has a first state, and more to
the second output waveguide than the first output waveguide when
the electrical control signal has a second state. The optical
deflector may be disposed on the same substrate as the first IC
chip, or may be disposed on an optical interconnect board. The
first control signal may be generated by any chip or component
within the processor, and may be generated by the first IC chip or
another chip located on the same substrate as the first IC
chip.
[0009] In the above example, the reception of the light signals may
be handled in a number of ways. In one configuration, each of the
first and second light receivers may receive an optical signal from
a single dedicated waveguide. In another case, each of the first
and second light receivers may receive its optical signal from one
of a plurality of waveguides that is adaptively selected during
operation by an optical deflector similar to that described above.
The latter configuration enables a large number of waveguides to be
replaced by a smaller number of bus-type waveguides that are shared
in a multiplexed manner.
[0010] A second exemplary embodiment of the present invention
encompasses a processor that is suitable for use as a computer
system, or a network server, or the like. The processor comprises
at least a first IC chip, a second IC chip, and a third IC chip,
each IC chip being mounted on a substrate, such as a component
board. Usually, the IC chips are mounted on separate substrates,
but two or more of the IC chips may be mounted on a common
substrate. The IC chips perform tasks in support of the operation
of the processor, the first IC chip receiving a signal in optical
form that is conveyed from one of the second and third IC chips.
The processor further comprises a first light receiver having an
optical input and generating a first electrical signal in relation
to the amount of light received at its optical input. The first
electrical signal is electrically coupled to the first IC chip, and
the first light receiver may be integrated onto either the first IC
chip or another chip. The processor further comprises a first light
transmitter that receives a second electrical signal from the
second IC chip and generates an optical signal at an optical output
in relation to the second electrical signal. The first light
transmitter may be integrated onto the second IC chip, or it may be
integrated onto another chip. The processor further comprises a
second light transmitter that receives a third electrical signal
from the third IC chip and generates an optical signal at an
optical output in relation to the third electrical signal. The
second light transmitter may be integrated onto the third IC chip,
or it may be integrated onto another chip. The processor further
comprises an optical deflector having a first optical input
optically coupled to a waveguide that enables light to be conveyed
from the first light transmitter, a second optical input optically
coupled to a waveguide that enables light to be conveyed from the
second light transmitter, an optical output optically coupled to
the optical input of the first light receiver, and an electrical
input that receives a first control signal in electrical form. The
optical deflector further has a first optical coupling efficiency
between its first optical input and its optical output, and a
second optical coupling efficiency between its second optical input
and its optical output. The first optical deflector makes the first
optical coupling efficiency greater than the second optical
coupling efficiency when the first control signal has a first
state, and makes the second optical coupling efficiency greater
than the first optical coupling efficiency when the first control
signal has a second state. The optical deflector may be disposed on
the same substrate as the first IC chip, or may be disposed on an
optical interconnect board. The first control signal may be
generated by any chip or component within the processor, and may be
generated by the first IC chip or another chip located on the same
substrate as the first IC chip.
[0011] In the above example, the transmission of the light signals
may be handled in a number of ways. In one configuration, each of
the first and second light transmitters couples its optical output
to a single dedicated waveguide. In another case, like that of the
first exemplary embodiment described above, each of the first and
second light transmitters may couple its optical signal to one (or
more) of a plurality of waveguides that is adaptively selected
during operation by an optical deflector, as described above. The
latter configuration enables a large number of waveguides to be
replaced by a smaller number of bus-type waveguides that are shared
in a multiplex manner.
[0012] Accordingly, it is an object of the present invention to
enable scalable-architecture computers and network servers to
process more information.
[0013] It is a further object of the present invention to provide a
large number of optical-signal interconnects among component boards
using a small number of light transmitters and/or light
receivers.
[0014] It is a further object of the present invention to reduce
the cost of implementing optical-signal interconnects in large
processors.
[0015] These objects and others will become apparent to one of
ordinary skill in the art from the present specification, claims,
and attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a perspective view of an exemplary processor
embodiment according to the present invention.
[0017] FIG. 2 shows a partial perspective view of a component board
and a first exemplary optical deflector that may be used in the
processor shown in FIG. 1 according to the present invention.
[0018] FIG. 3 shows a top plan view of the first exemplary optical
deflector shown in FIG. 2 according to the present invention.
[0019] FIG. 4 shows a cross-sectional view of a second exemplary
optical deflector that may be used in the processor shown in FIG. 1
according to the present invention.
[0020] FIG. 5 shows a partial perspective view of the second
exemplary optical deflector shown in FIG. 4 according to the
present invention.
[0021] FIG. 6 shows a schematic diagram of an exemplary optical
wiring architecture that may be used in the processor shown in FIG.
1 according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0022] FIG. 1 shows a perspective view of a processor embodiment of
the present invention at 100. Processor 100 comprises a plurality
of component boards 120 mechanically coupled to a main optical
backplane 110, preferably in a detachable manner. Optical signals
are routed among component boards 120 as described below in greater
detail. Component boards 120 may be component boards of any
electro-optic-based system, such as daughter boards of a computer
system or processor blades of a network server. A component board
120 comprises a base substrate 122, a plurality of integrated
circuit chips (IC chips) 130, a plurality of opto-electric devices
135 formed on one or more chips, a network of electrical traces 125
formed in and/or on base substrate 122, a plurality of optical
deflectors 140 formed on base substrate 122, and a plurality of
optical waveguides 150 formed on base substrate 122. For visual
clarity in FIG. 1, some of these elements and their reference
numbers are omitted for the three lower boards 120. Main optical
backplane 110 comprises a base substrate 112, a plurality of
optical waveguides 115 formed on or near the top surface of
substrate 112 to interconnect optical signals among component
boards 120, and optionally a network of electrical traces to
interconnect electrical signals among component boards 120, as
explained below in greater detail.
[0023] The network of electrical traces 125 on each component board
120 electrically interconnects IC chips 130 to one another, and
preferably interconnects selected IC chips to opto-electric devices
135 and optical deflectors 140. The IC chips 130 are interconnected
by traces 125 according to the desired function performed by the
chips and the system. Opto-electric devices 135, optical deflectors
140, waveguides 150, and waveguides 115 provide board-to-board
optical-signal interconnections among component boards 120. Each
opto-electric device 135 may comprise a light transmitter or a
light receiver, and each chip of opto-electric devices 135 may
comprise one or more light transmitters, one or more light
receivers, or a combination of light transmitter(s) and light
receiver(s). A signal generated in a first IC chip 130 on the top
component board 120 may be optically communicated to a second IC
chip 130 on a middle component board 120 in the following manner.
The first IC chip 130 on the top component board 120 generates a
first electrical information signal, which is electrically coupled
to a first light transmitter device 135 located on the top
component board 120. The first light transmitter device 135
converts the first electrical information signal to a first optical
information signal, and couples it to a first deflector 140. The
first deflector 140 then routes the first optical signal to a first
waveguide 150 that will convey the optical signal to a first
waveguide 115 on main optical backplane 110, which in turn will
convey the optical signal to a first light receiver on the middle
component board 120 for the second IC chip 130. Optical signals
between waveguides 150 and 115 may be coupled by conventional
mirrors or gratings formed in main optical backplane 110. The first
deflector 140 receives a first control signal that instructs it to
select the first waveguide 150 for routing the first optical signal
to the first light receiver. The first control signal is generated
by an electrical component of processor 100, such as an IC chip on
the top component board 120, which can be the first IC chip
130.
[0024] On the middle component board 120, a second waveguide 150
receives the first optical signal from the first waveguide 115 of
main optical backplane 110. Second waveguide 150 may convey the
first optical signal directly to the first light receiver device
135 (which is located on a second chip of opto-electric devices 135
on the middle component board 120), or by way of a second deflector
140 located on the middle component board 120. In the first case,
the first light receiver device 135 converts the optical signal to
an electrical signal, which is then electrically coupled to the
second IC chip 130. In the second case, the second deflector 140
selects the second waveguide 150 from a number of other waveguides
150 (which are optically coupled to other respective waveguides
115) before coupling it to the first light receiver device 135 for
conversion. The second deflector 140 receives a second control
signal that instructs it to select the second waveguide 150. The
second control signal is generated by an electrical component of
processor 100, such as an IC chip on the middle component board
120, which can be the second IC chip 130. The first and second
control signals may be coordinated by sending control signals
through one or more optical waveguides 115 that are dedicated to
that purpose, or by sending control signals through optional
electrical traces 117 of main optical backplane 110, which in turn
are coupled to selected traces 125 on component boards 120.
[0025] In a similar manner, the first information signal generated
by first IC chip 130 on the top component board 120 may be
optically communicated to a third IC chip 130 on the bottom
component board 120. As before, the first electrical information
signal is electrically coupled to the first light transmitter
device 135 located on the top component board 120, and the first
light transmitter device converts the first electrical information
signal to a first optical information signal and couples the latter
to the first deflector 140. The first deflector 140 then routes the
first optical signal to a third waveguide 150 that will convey the
first optical signal to a second waveguide 115 on main optical
backplane 110, which in turn will convey the first optical signal
to a second light receiver device 135 on the bottom component board
120 for the third IC chip 130. The first control signal to the
first deflector 140 instructs the deflector to select the third
waveguide 150 instead of the first waveguide 150. On the bottom
component board 120, a fourth waveguide 150 receives the first
optical signal from the second waveguide 115 of main optical
backplane 110. Fourth waveguide 150 may convey the first optical
signal directly to the second light receiver device 135 (which is
located on a third chip of opto-electric devices 135 on the bottom
component board 120), or by way of a third deflector 140 located on
the bottom component board 120. In the first case, the second light
receiver device converts the optical signal to an electrical
signal, which is then electrically coupled to the third IC chip
130. In the second case, the third deflector 140 selects the fourth
waveguide 150 from a number of other waveguides 150 (which are
optically coupled to other respective waveguides 115) before
coupling it to the second light receiver device for conversion. The
third deflector 140 receives a third control signal that instructs
it to select the fourth waveguide 150. The third control signal is
generated by an electrical component of processor 100, such as an
IC chip on the bottom component board 120, which can be the third
IC chip 130. The first and third control signals may be coordinated
by sending control signals through one or more optical waveguides
115 that are dedicated to that purpose, or by sending control
signals through optional electrical traces 117 of main optical
backplane 110, which in turn are coupled to selected traces 125 on
component boards 120.
[0026] In this manner, a first information signal generated from an
IC chip 130 on top component board 120 can be optically transmitted
to a selected chip on one of the other component boards by the
coordination of the control signals. In a similar manner
information signals generated by IC chips 130 on the other
component boards 120 may be optically transmitted to top component
board 120 and to the other component boards 120. For this, each
component board has an array of light transmitters, an array of
light receivers, and a plurality of optical deflectors 140 and
waveguides 150. Exemplary arrangements of these components are
provided below after exemplary embodiments of optical deflector 140
and waveguides 150 are described.
[0027] FIG. 2 shows a partial perspective view of component board
120 that shows the features of an exemplary embodiment 140-1 of
deflector 140 and waveguides 150. For the purpose of visual
clarity, the chip for opto-electric devices 135 is offset upwards
from its normal position, as shown by the small vertical dashed
lines below it. Component board 120 comprises a component layer 121
at the top of the board. Deflector 140-1 and four waveguides
150a-150d are embedded in layer 121. Waveguide 150a is disposed
between the chip of opto-electric devices 135 and deflector 140-1,
and has a first end disposed under the attachment area for the chip
of opto-electric devices 135 and a second end disposed adjacent to
deflector 140-1. A reflector 152 is disposed at the first end of
waveguide 150a, and serves to couple light between waveguide 150a
and an opto-electric device 135, which may be a light transmitter
or a light receiver. (It is possible for reflector 152 to couple
light between waveguide 150a on the one side, and a small number of
opto-electric devices 135 on the other side closely grouped
together on the chip). Deflector 140-1 is a prism-type deflector
and comprises a first optical surface 141 facing towards the second
end of waveguide 150a to couple light therewith, a second optical
surface 142 located opposite to first optical surface 141 to couple
light beams in or out of surface 142 at a plurality of directions,
and a body 145 of opto-electric material disposed between first
optical surface 141 and second optical surface 142. Three
waveguides 150b-150d are disposed between second optical surface
142 and the attachment edge of component board 120 that attaches to
main optical backplane 110. Deflector 140-1 is configured and
operated to bend the light passing through it principally along
three possible paths, and each of waveguides 150b-150d is located
to couple light between itself and deflector 140-1 along a
respective one of these paths.
[0028] More specifically, light may flow through deflector 140-1 in
either direction along the three paths. In the case that a light
transmitter is optically coupled to waveguide 150a (through
reflector 152), light flows through waveguide 150a to deflector
140-1, and is then directed principally along one of the three
paths by deflector 140-1 to one of waveguides 150b-150d. From
there, the light is directed to main optical backplane 110. In this
case, waveguide 150a may be called an input waveguide, and each of
waveguides 150b-150d may be called an output waveguide. In the case
that a light receiver is optically coupled to waveguide 150a,
deflector 140-1 receives light at its second optical surface from
at least one of the waveguides 150b-150d, deflects the path of the
received light toward waveguide 150a. From there, the light
propagates in waveguide 150a toward opto-electric device 135. In
this case, waveguide 150a may be called an output waveguide, and
each of waveguides 150b-150d may be called an input waveguide.
Deflector 140-1 may also receive light at its second optical
surface 142 from the other waveguides, but this light is deflected
in a manner that prevents it from substantially entering waveguide
150a. Since light may flow in either direction in waveguides
150a-150d, they may be given the following more general names:
inner coupling waveguide 150a (since it is located more toward the
interior of component board 120), and outer coupling waveguides
150b-150d (since they are located at the attachment edge of
component board 120).
[0029] Deflector 140-1 also comprises a top electrode 143 disposed
on the top surface of opto-electric body 145, and preferably a
bottom electrode 144 disposed on the bottom surface of
opto-electric body 145. (In place of bottom electrode 144, an
electrode may be formed on the top of substrate 122 or therein,
below component layer 121.) Top electrode 143 comprises a
polygon-shape having two non-parallel sides, one such side facing
first optical surface 141 and inner waveguide 150a, and the other
such side facing second optical surface 142 and the outer
waveguides 150b-150d. A triangle is shown in the figure. If bottom
electrode 144 is used, it preferably has the same shape as top
electrode 143, and is aligned opposite to it. An electric field is
established between electrodes 143 and 144 by applying a voltage
between the electrodes through electrical traces 125a and 125b,
which are coupled to electrodes 143 and 144, respectively, through
respective vias. The electric field causes the portion of body 145
that is between the electrodes to undergo a change in refractive
index, thereby creating a spatial change in refractive index that
underlies each of the polygon sides of the electrodes. Because the
two polygon sides facing optical surfaces 141 and 142 are not
parallel, the spatial change in refractive index will cause bending
of the light as it passes under each polygon side of electrode 143,
substantially according to the well-known Snell's law. The result
is a deflection of the light's path through deflector 140-1. The
degree of deflection depends upon the change in refractive index,
which in turn depends upon the polarity and the magnitude of the
applied voltage. The workings of prism deflectors are known to the
optics arts, and a detailed description thereof is not needed for
one of ordinary skill in the optics art to make and use the present
invention.
[0030] The material of body 145, the shape of electrodes 143 and
144, and the distances between second optical surface 142 and
waveguides 150b-150d are preferably selected such that: [0031] 1.
light is principally coupled between deflector 140-1 and waveguide
150b when a voltage of +M (or alternatively -M) is applied between
electrodes 143 and 144, [0032] 2. light is principally coupled
between deflector 140-1 and waveguide 150c when zero volts is
applied between electrodes 143 and 144, and [0033] 3. light is
principally coupled between deflector 140-1 and waveguide 150d when
a voltage of -M (or alternatively +M) is applied between electrodes
143 and 144. M may have the value of 5 to 10 volts, given that
recent polymer-based electro-optic materials have electro-optic
coefficients of over 100 picometers per volt (for example, see the
chromophoric organic electro-optic materials from Lumera, and U.S.
Pat. No. 6,716,995). Instead of using the voltages +M, 0, and -M to
set the beam deflection to select waveguides 150b-150d, one may use
the voltages 0, +1/2M, +M, or 0, -1/2M, -M (i.e., all voltages of
one polarity).
[0034] FIG. 3 shows a top plan view of deflector 140-1 and
waveguides 150a-150d and the three optical paths that can be
established between deflector 140-1 and waveguides 150b-150d. The
deflection angle of the paths to waveguides 150b and 150d may be as
small at 0.5 degrees in either direction. Waveguides 150b and 150d
have small curvatures to aid in steering the deflected light back
into a line substantially parallel with the optical axis of
waveguide 150c. The curvature of waveguides 150b and 150d may be
around 5 degrees. Waveguides 150a-150d and deflector 140-1 may be
formed by conventional waveguide processing steps without undue
experimentation.
[0035] When deflector 140-1 receives light from opto-electric
device 135, first optical surface 141 provides an optical input for
the deflector to receive an optical signal, and second optical
surface 142 provides three optical outputs at the exit points of
the three optical paths to waveguides 150b-150d, as shown at
reference numbers P1, P2, and P3 in FIG. 3. The first control
signal may have three states, each state to select a respective
optical path and a respective optical output P1-P3. In the first
state, deflector 140-1 couples the received optical signal more
toward optical output P1 than to optical outputs P2 and P3, so that
most of the optical signal goes to waveguide 150b. In the second
state, deflector 140-1 couples the received optical signal more
toward optical output P2 than to optical outputs P1 and P3, so that
most of the optical signal goes to waveguide 150c. And in the third
state, deflector 140-1 couples the received optical signal more
toward optical output P3 than to optical outputs P1 and P2, so that
most of the optical signal goes to waveguide 150d.
[0036] When deflector 140-1 conveys light to opto-electric device
135, first optical surface 141 provides an optical output for the
deflector to output an optical signal, and second optical surface
142 provides three optical inputs at the entry points of the three
optical paths from waveguides 150b-150d, again as shown at
reference numbers P1, P2, and P3 in FIG. 3. The prism deflector
provides a respective variable-coupling efficiency between each
optical input P1-P3 and the optical output. Each of the coupling
efficiencies changes as the voltage to electrode 143 is varied. The
first control signal coupled to electrode 143 may have three
states, one state to select a respective optical path and a
respective optical input P1-P3 by increasing the coupling
efficiency to that optical input with respect to the other coupling
efficiencies. In the first state, deflector 140-1 makes the
coupling efficiency to optical input P1 significantly greater than
the coupling efficiencies to optical inputs P2 and P3. In the
second state, deflector 140-1 makes the coupling efficiency to
optical input P2 significantly greater than the coupling
efficiencies to optical inputs P1 and P3. And in the third state,
deflector 140-1 makes the coupling efficiency to optical input P3
significantly greater than the coupling efficiencies to optical
inputs P1 and P2.
[0037] As a closing note to the discussion of FIGS. 2 and 3, the
electo-optic device 135 indicated in FIG. 2 has its electrical
terminals coupled to chip 130a by way of the electrical traces
shown between chip 130a and the chip for device 135. If device 135
is a light transmitter, these traces provide the electrical signal
that will be converted to the optical signal. If device 135
comprises a light receiver, these traces provide the electrical
signal that has been converted from the optical signal.
[0038] FIG. 4 shows a cross-sectional view of a second embodiment
240 of an exemplary optical deflector according to the present
invention, and FIG. 5 shows a partial perspective view. Optical
deflector 240 is useful when an optical signal is to be
simultaneously transmitted to two IC chips, or to only one of two
IC chips. Deflectors 240 and 140-1 may be used on the same
substrate, and may be coupled in series (that is, an output of
deflector 140-1 may be coupled to an input of deflector 240, and an
output of deflector 240 may be coupled to an input of deflector
140-1). In optical deflector 240, inner waveguide 150a is not used,
and two outer waveguides 150b and 150c are used. Waveguide 150c is
disposed above waveguide 150b, with each having a first end
disposed under or near the chip-holding device 135, and a second
end disposed near the attachment edge of substrate 120 to main
optical backplane 110. In the figures, the core bodies of
waveguides 150b and 150c are shown with clear areas, and the
cladding layers are shown with stippled-fill patterns. The
waveguides are preferably disposed such that their core bodies are
separated by .about.15 microns or more for single mode waveguides,
and by .about.50 microns or more for multi-mode waveguides. A
sub-layer 121b of component layer 121 described below can be used
to provide the desired spacing distance (it preferably has a
refractive index equal to or less than that of the cladding
layers). While FIG. 5 shows the waveguide 150c being disposed above
and directly over waveguide 150d in a parallel manner, it may be
appreciated that waveguide 150c may still lie above waveguide 150d
but be in a non-parallel relationship. As explained below, the
construction of optical deflector 240 is based on Snell's law and
the actions of total internal reflection, partial reflection, and
partial transmission.
[0039] Optical deflector 240 comprises an angled reflector 245 and
a variable reflector 250. Angled reflector 245 is disposed at the
left end of waveguide 150b; it reflects light between the core body
of waveguide 150b and the bottom surface of variable reflector 250.
Angled reflector 245 preferably comprises a metal layer formed over
a beveled side surface of a sub-layer 121a of component layer 121,
the side surface being beveled with respect to the top surface of
base substrate 122 and the top surface of component layer 121, and
with respect to the optical propagation axis of waveguide 150b. As
used herein, the adjective "beveled" means formed to a bevel angle
with respect to a reference surface or reference line (e.g., an
optical propagation axis of a waveguide), with the bevel angle
being any angle except 90 degrees (right angle). Angled reflector
245 may be formed by the following sequence of processing steps:
forming sub-layer 121a using a photo-imageable polymer;
photo-exposing the sub-layer through a gray-scale mask that defines
the beveled side surface; developing the exposed layer to form the
beveled side surface; and then forming a metal layer over the
beveled side surface. Thereafter, the layers of waveguide 150b may
be formed, followed by the formation of sub-layer 121b, which acts
as a planarizing layer as well as a spacer layer between waveguides
150b and 150c. In this way, the metal surface of angled reflector
245 makes an inclined angle with respect to the top surface of base
substrate 122. It is also possible to make angled reflector 245 by
the steps of: initially forming sub-layer 121a as a slab waveguide
comprised of photo-imageable core and cladding layers having
closely matched photo-chemistries; photo-exposing the slab
waveguide through a gray-scale mask that defines both the beveled
side surface and waveguide 150b; developing the exposed layer to
form the beveled side surface and waveguide 150b; and then forming
a metal layer over the beveled side surface.
[0040] Variable reflector 250 comprises a top surface 251 facing
device 135, a bottom surface 252 facing towards the angled
reflector 245, a first side surface 254 facing the first end of
waveguide 150c, a body 255 of electro-optic material disposed
between top surface 251 and bottom surface 252, and a body 260 of
high-refractive index material disposed between top surface 251 and
bottom surface 252 and adjacent to body 255 of electro-optic
material. An interface surface 253 is disposed between bodies 255
and 260, and is beveled with respect to the top surface of base
substrate 122, with respect to the top surface of component layer
121, and with respect to the optical propagation axis of waveguide
105c. In other words, interface surface 253 is formed to a bevel
angle with respect to the top surfaces of substrate 122 and
component layer 121, and the optical propagation axis of waveguide
105c, with the bevel angle being any angle except 90 degrees.
Preferably, the bevel angle is within one or two degrees of 45
degrees (45.degree.), and more preferably within a half-degree of
45 degrees. Interface surface 253 is preferably planar. The
refractive index of body 260 is substantially greater than the
intrinsic refractive index of body 250 of electro-optic material,
preferably being at least 10% higher. As used herein, the intrinsic
refractive index of an electro-optic material is the refractive
index of the material when no electric field is present in the
material. The refractive index of body 260 can also be higher than
the intrinsic refractive index by 20% or more, 25% or more, and 35%
or more.
[0041] FIG. 5 shows a partial perspective view of optical deflector
240 and waveguides 150b and 150c. Sub-layer 121c of component layer
121 has been omitted for visual clarity. As can be seen therein,
variable reflector 250 further comprises a second side surface 256
and a third side surface 257 that are oriented substantially
transverse to first side surface 254. A first electrode 258 is
disposed on second side surface 256 and a second electrode 259 is
disposed on third side surface 257. Electrodes 258 and 259 apply an
electric field to body 255 of electro-optic material in relation to
the first control signal. The electric field changes the refractive
index of body 255, and both the field and the refractive index vary
with the value of the first control signal. Electrodes 258 and 259
may be spaced from one another by a distance on the order of the
width of the core body in waveguide 150c, typically ranging from 5
microns to 10 microns for single mode waveguides, and 25 microns to
50 microns for multi-mode waveguides. The electrodes may be made of
tungsten to minimize reflections from their surfaces. Bodies 255
and 260 can be formed by conventional photolithographic methods. To
achieve the bevel of interface surface 253, one may first form a
rectangular strip of electro-optic material over layer 121b,
thereafter form a metal mask for laser ablation, and then cut the
bevel with laser ablation with the laser light at an angle (e.g.,
45-degree angle) to the top surface of base substrate 122. Also,
plasma etching through a tapered mask may be used, with the tapered
mask comprising a photoresist that has been exposed through a
gray-scale mask. Dicing using a blade with beveled edge is also
possible. After interface surface 253 has been formed, body 260 may
be formed and patterned by conventional process steps. Thereafter,
the electrodes may be formed by conventional sputtering and etching
steps.
[0042] Variable reflector 250 works as follows. We take the case of
opto-electric device 135 comprising a light transmitter that
directs a beam of light toward the top surface of component layer
121, and specifically toward top surface 251 and body 260 of
high-refractive-index material. The intrinsic refractive index of
body 255, the refractive index of body 260, and the bevel angle of
interface surface 253 are selected such that interface surface 253
is near or at the initial point of total internal reflection (i.e.,
critical angle) for light emitted from the light transmitter (i.e.,
for light directed perpendicular to the top surfaces of layer 121
and base substrate 122). This selection can be done by the
application of Snell's law and computer simulation programs
available for purchase or on the Internet (e.g.,
http://www.physics.nwu.edu/ugrad/vpl/optics/snell.html). Then, by
changing the refractive index of body 255, as directed by the first
control signal, the majority of the light from device 135 can be
reflected off interface surface 253 to the first end of waveguide
150c through side surface 254, or the majority of the light can be
transmitted through the interface surface 253 to exit bottom
surface 252, where it strikes angle reflector 245 and enters the
first end of waveguide 150b. Also, the refractive index can be
changed to cause the light to split at interface surface 253 such
that approximately one-half is reflected to waveguide 150c and
approximately one-half is transmitted to waveguide 150b.
[0043] In this manner, top surface 251 of variable reflector 250
acts as an optical input of deflector 240, the first side surface
254 acts as a first optical output of deflector 240, and bottom
surface 252 and angled reflector 245 act as a second optical output
of deflector 240. Furthermore, a first coupling efficiency is
provided between the optical input and the first optical output, a
second coupling efficiency is provided between the optical input
and the second optical output, and the variation in the refractive
index of electro-optic body 255 enables the relative values of
these coupling efficiencies to change in relation to the state of
the first control signal. The first coupling efficiency may be
greater than the second coupling efficiency in one state of the
first control signal, less than the second coupling efficiency in a
second state, and substantially equal to the second coupling
efficiency in a third state.
[0044] We give the following example. Body 255 has a refractive
index of 1.39 with no electric field. The refractive index can be
changed to a value of 1.38 with the application of negative voltage
to electrode 258 with respect to electrode 259, and can also be
changed to a value of 1.41 with the application of positive voltage
to electrode 258 with respect to electrode 259. On the other hand,
body 260 has a refractive index of 1.95 (40% higher than the
intrinsic refractive index of body 255). When body 255 is caused to
have a refractive index of 1.38, 78% of the light is reflected off
interface surface 253 to waveguide 150c and 22% is transmitted
through the surface to waveguide 150b. In this state, the first
coupling efficiency is 78% and is greater than the second coupling
efficiency (22%). When body 255 is caused to have a refractive
index of 1.39, 48% of the light is reflected off interface surface
253 to waveguide 150c and 52% is transmitted through the surface to
waveguide 150b. In this state, the first coupling efficiency is 48%
and is substantially equal to the second coupling efficiency (52%).
And when body 255 is caused to have a refractive index of 1.41, 30%
of the light is reflected off interface surface 253 to waveguide
150c and 70% is transmitted through the surface to waveguide 150b.
In this state, the first coupling efficiency is 30% and is less
than the second coupling efficiency (70%). In general, the
photo-detectors that receive this light can be designed such that a
value of 30% lies below the detection threshold of the
photo-detector, and that a value of 50% lies above the detection
threshold. The first control signal may have three states to select
among the three above divisions of the light beam from device
135.
[0045] The high-refractive-index material for body 260 may be
provided by the OptiNDEZ A14 material manufactured by Brewer
Science Inc. This is a pure polymer-based material. As another
option, one may use a conventional polymer that has been loaded
with micro particles of a high-refractive crystal, such as
sapphire. The electro-optical material in the above example may be
a chromophoric organic electro-optic material from Lumera, or one
described in U.S. Pat. No. 6,716,995 or other recent patents
disclosing new polymers with high electro-optic coefficients.
Currently, one can readily obtain a polymer-based electro-optic
material with an electro-optic coefficient of about 120 picometers
per volt, which can yield a change from 1.39 to 1.405 with the
application of about 92 volts per micron between electrodes 258 and
259. A high voltage driver chip would be needed to drive the
electrodes, and such chips are commercially available. The first
control signal may be provided as an input to such a chip to
generate a voltage amplified version thereof. In the near future,
it is expected that the chromophoric organic electro-optic
materials will have coefficients of several hundred picometers per
volt, which will significantly reduce the voltage that needs to be
applied across electrodes 258 and 259.
[0046] In the above cases where 52% and 70% of the light is
transmitted through to angled reflector 245, the transmitted light
beam makes an angle of between 38 degrees and 33 degrees with a
line vertical to the top surface of substrate 122. This is an
average angle of approximately 35 degrees. With this average angle,
angled reflector 245 should be disposed to the side of interface
surface 253 to receive the angled light, and the beveled surface of
angled reflector 245 should be around 27.5 degrees (which is less
than 45 degrees by half the value of 35 degrees). The average angle
of 35 degrees (and the range from 38 degrees to 33 degrees) can be
reduced by disposing high refractive index material between the
bottom surface 252 of variable reflector 250 and angled reflector
245.
[0047] While optical deflector 240 has been described with
opto-electric device 135 being a light transmitter, it may be
appreciated that device 135 may be a light receiver, and that the
direction of light in deflector 240 may be reversed. In other
words, each of waveguides 150b and 150c may couple light beams to
the interface surface 253, and a majority of one of the light beams
may be coupled to device 135 based on the refractive index of
electro-optic body 255. In this case, top surface 251 of variable
reflector 250 acts as an optical output of deflector 240, the first
side surface 254 acts as a first optical input of deflector 240,
and bottom surface 252 and angled reflector 245 act as a second
optical input of deflector 240. Furthermore, a first coupling
efficiency is provided between the first optical input and the
optical output, a second coupling efficiency is provided between
the second optical input and the optical output, and the variation
in the refractive index of electro-optic body 255 enables the
relative values of these coupling efficiencies to change in
relation to the state of the first control signal in the same
manner as the coupling efficiency changed in the above case where
the light flowed in the opposite direction. (In other words,
optical deflector 240 is a linear system.) The first coupling
efficiency may be greater than the second coupling efficiency in
one state of the first control signal, less than the second
coupling efficiency in a second state, and substantially equal to
the second coupling efficiency in a third state.
[0048] In FIGS. 4 and 5, the top surface of high-refractive body
260 has been shown to be substantially parallel to the top surfaces
of component layer 121 and base substrate 122. However, the top
surface of body 260 may be inclined to create a more shallow
incident angle of light from device 135 onto interface surface 253.
In this case, interface surface 253 would be inclined at an angle
of less than 45 degrees with respect to the top surface of base
substrate 122.
[0049] As another variation, interface surface 253 can be inclined
at an angle substantially greater than 45 degrees with respect to
the top surface of base substrate 122, such as 50 degrees and 55
degrees. This would enable one to achieve the initial point of
total internal reflection with less of a difference between the
refractive indices of bodies 255 and 260. However, the steeper
angle causes the light reflected from interface surface 253 to
angle downward into component layer 121 toward base substrate 122,
rather than being substantially parallel to the top surface of base
substrate 122. This can be addressed by positioning waveguide 150c
at a level in component layer 121 that is lower than that shown in
FIGS. 4 and 5, so that the left end of the waveguide can capture
the downward-angled light. If needed, an angled deflector similar
to that of angled deflector 245 can be positioned at the left end
of waveguide 150c, or, more simply, the face of high-refractive
body 260 at first side surface 254 may be beveled in order to bend
the light from interface surface 253 to a horizontal direction or
more a horizontal direction when it exits surface 254.
[0050] Claims of the present application encompass the above
variations.
[0051] Having thereby described exemplary embodiments of deflector
140 and waveguides 150, we return to the global view of the
processor shown in FIG. 1. As we indicated before, optical
connections between each of the boards may be configured by
deflectors 140, with optical routing done through main optical
backplane 110. In FIG. 6, we show a schematic diagram of the
optical wiring architecture that may be used in processor 100,
which shows one way in which the optical waveguides 115 of
backplane 110 may be interconnected with waveguides 150b-150d. The
four component boards are indicated at reference numbers 120-1
through 120-4. At each end of waveguide 115, a mirror or grating
element is placed to optically couple the end of the waveguide to
one of waveguides 150b-150d in a component board. Twelve optical
interconnects are provided, two interconnects between each pair of
component boards 120 (one transmission and one reception). Only
eight waveguide channels are needed in backplane 110 to implement
the twelve interconnects since the six shortest optical
interconnects may all be placed in two waveguide channels. Only one
pair of a light transmitter and a light receiver is shown for each
component board 120 in FIG. 6 for visual clarity. In practice, each
board would have multiple pairs of transmitters/receivers, and the
wiring diagram shown in FIG. 6 would be duplicated for each
additional pair. As an alternative to the architecture shown in
FIG. 6, one can use optical bus waveguides for waveguides 115, each
of which has a bidirectional optical coupler to each component
board. This would reduce the number of waveguides 115 to four (one
for the receiver of each component board). However, bidirectional
optical couplers often degrade the optical signal as it propagates
through the waveguide, and so signal strength in the waveguide may
become an issue.
[0052] While we have focused the description on board-to-board
interconnects, it may be appreciated that the optical
communications described herein may be applied within a single
board, such as chip-to-chip communications. Claims of the present
application encompass this application as well. In addition, one
may place some or all of deflectors 140 in main optical backplane
110, with control signals for the deflectors being generated within
backplane 110 and/or within the component substrates. Also, one may
place some or all of the deflectors on intermediate boards that
interface between the component boards 120 and main optical
backplane 110. Claims of the present application encompass these
variations as well.
[0053] While the present invention has been particularly described
with respect to the illustrated embodiments, it will be appreciated
that various alterations, modifications and adaptations may be made
based on the present disclosure, and are intended to be within the
scope of the present invention. While the invention has been
described in connection with what are presently considered to be
the most practical and preferred embodiments, it is to be
understood that the present invention is not limited to the
disclosed embodiments but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the scope of the appended claims.
* * * * *
References